docs: def register_neurite_feature(name, func):
      '''Register a feature to be applied to neurites
  
      Parameters:
          name: name of the feature, used for access via get() function.
          func: single parameter function of a neurite.
      '''
      if name in NEURITEFEATURES:
          raise NeuroMError('Attempt to hide registered feature %s' % name)
  
      def _fun(neurites, neurite_type=_ntype.all):
          '''Wrap neurite function from outer scope and map into list'''
          return list(func(n) for n in _ineurites(neurites, filt=_is_type(neurite_type)))
  
      NEURONFEATURES[name] = _fun